Jim Weirich observes that Pythonistas and Rubyists bring different assumptions to the table:

Python follows C++ and Java in using "." as a structure selector operation, while Ruby is more closely attuned to Smalltalk's message sending paradigm. Both approaches work and are interally consistent, but be prepared for surprises if you try to interpret one using the assumptions of the other.

Jeffrey Shell blogs on Python's philisophy of simplicity and then references a comp.lang.python post that goes over his assessment of Ruby vs Python in great detail. In the blog post, he extols the Python module system and quotes Tim Peters' "The Zen of Python". The newsgroup post goes over the stuff in Ruby that is matched by Python 2.2.

Hans Nowak has a series of 3 (so far) comparison posts. Here's some things I picked up:

first post

He sort of likes creative use of punctuation in Ruby. I'm the same. The use of ? and ! seem good to me.

second post

Ruby yield works on closures.
Ruby can define methods on instances.

third

He's not sure what the big deal is about procedure objects (closures). First classness.